/Engine/Source/Runtime/Engine/Classes/Engine/StreamableManager.h
Gets list of handles that are directly referencing this asset, returns true if any found. Combined Handles will not be returned by this function.
bool GetActiveHandles ( const [FSoftObjectPath](API\Runtime\CoreUObject\UObject\FSoftObjectPath) & Target, [TArray](API\Runtime\Core\Containers\TArray)< [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [FStreamableHandle](API\Runtime\Engine\Engine\FStreamableHandle) >> & HandleList, bool bOnlyManagedHandles ) const